1. Field of the Invention
The present invention relates to video receivers, and more particularly, to multi-tuner receivers with cross talk reduction.
2. Background of the Invention
Increasingly, televisions and cable set top boxes for receiving cable television and satellite signals, including broadcast programming and Internet services, can provide the ability to receive multiple channels simultaneously. This capability permits features such as simultaneous television and Internet service, picture-in-picture displays, and distributing service to multiple rooms in one household.
The set top boxes and televisions for processing multiple channels require multi-tuner receivers, which extract multiple cable or satellite signals. The multi-tuner receivers select the desire channels for demodulation and further signal processing. An architecture for set top boxes or televisions requiring multiple tuners uses a passive splitter to receive and distribute an RF signal to multiple tuners. An alternative architecture for set top boxes or televisions requiring multiple tuners uses a low noise amplifier (LNA) to amplify an incoming RF signal and distribute the signal to multiple tuners. In general, there may be one or multiple outputs for the LNA with each output driving one tuner or multiple tuners in parallel. The LNA architecture avoids loss and reduction in noise figure that results when a passive splitter is used to drive multiple channels.
In either case, one difficulty associated with the use of multi-tuner receivers relates to the leakage of electromagnetic energy among tuners, which is often referred to as cross talk. Various signals generated in one tuner can leak from the tuner input to an LNA output, and from the LNA output to another tuner input. Such leakage can result in undesired levels of spurious signals at the output of the second tuner. This type of cross talk can also occur in a multi-tuner system using a passive splitter at the front end, since passive splitters also have finite isolation.
What is needed is a cost-effective multi-tuner receiver with cross talk reduction.